This invention relates to methods for controlling the reel-up operation of paper webs, particularly in Pope-type reel-up apparatus.
Pope-type reel-up apparatus include a reeling cylinder by which power is provided to a web reel being formed on a reeling drum through a nip formed between the periphery of the reeling cylinder and the periphery of the web reel being formed. In the reeling operation, the inner section of the web reel is formed on the reeling drum which is held on primary forks or the like whereupon the reeling drum and section of the web reel formed thereon are removed to secondary forks on which the final steps of the reeling operation are carried out. The loading of the power-transmitting nip is at least mainly provided by power equipment coupled to the primary and secondary forks.
Pope-type reel-up apparatus are commonly used for reeling paper web from equipment such as paper machines, coating machines, supercalenders and printing machines. In such apparatus, the web is reeled onto a drum and the web reel being formed is pressed against a Pope-type or reeling cylinder over a sector of which the web runs and which rotates at a peripheral speed which corresponds to the desired web speed. Before the web reel is completed, a new reeling drum may be brought into nip contact with the Pope cylinder after the reeling is accellerated to the proper running speed. As soon as the web reel attains the desired diameter, it is separated from the Pope cylinder so that its rotational speed decreases causing a web loop to form between the new reeling drum and the completed web reel. This loop is guided such, for example, as by means of a compressed air jet, to be wound around the new reeling drum whereupon the web is torn from the completed web reel.
In connection with the state of the art, reference is made to U.S. Pat. Nos. 2,176,198, 2,703,683, 3,116,031, 3,191,883, 3,202,374, 3,258,217 and 3,743,199.
A problem inherent in high speed web reeling operations using Pope-type or similar reel-up apparatus, is that folds are created in the inner layers of the web reels so that their bottom sections must be discarded. This problem is especially serious in connection with the reeling-up of LWC and SC paper qualities. The amount of such rejects may be as high as 2 to 3% which causes considerable economical loss to the paper mill. The main reason for the formation of such folds or wrinkles in the inner layers of the web reels is the variation of hardness or density in the bottom part of the reels which, in general, is caused by uncontrolled variations of the linear loading at the nip formed between the paper reel and the Pope cylinder and, additionally, by variations of the tightness of the paper web as discussed below.
Two main factors influence the hardness or density distribution of a paper or web reel reeled by a Pope-type reel-up apparatus, namely, firstly, the linear loading between the reeling cylinder and the paper reel and, secondly, the tightness of the web during the reeling operation which is a function of the speed differential between the calander and the reel-up apparatus. Uncontrolled variations in the hardness distribution with discontinuities therein cause problems in subsequent steps in the reeling-up operation and, in the worst case, tears and folds are created near the bottom of the reel. The present invention has as its main object the solution to these drawbacks caused by uncontrolled variations in the linear loading between the paper reel and the Pope cylinder.